• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.989-994
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• 2005

The treatment efficiency and the degradation characteristics of humic acid were investigated in three processes-GAC adsorption, Ozone alone and Ozone/GAC hybrid process, in which $UV_{254}$, DOC, molecular size distribution and surface change of GAC were evaluated. DOC removal rate in Ozone/GAC hybrid profess(ca. 80%) was higher than the arithmetic sum of Ozone alone(38%) and GAC adsorption(19%). This result approves that the combined Ozone/GAC hybrid process brings synergistic effects on DOC removal from the HA containing water. $UV_{254}$ decrease rate was also at the highest in Ozone/GAC hybrid process from the three processes. It may be interpreted that the granular activated carbon in Ozone/GAC hybrid process acts as not only an adsorbent but also a catalyst for ozonation, and futhermore offers an additional reaction site between adsorbed organic matter and ozone. In the study of molecular sire distribution, there was no significant change of molecular size distribution in the GAC adsorption process during the reaction time of 120 min. In Ozone alone process, the fraction of molecular size over 30 kDa was decreased a little at the beginning and left constant after 10 min. But in Ozone/GAC hybrid process, the molecules size over 30 kDa of HA was significantly decreased from 36.3% to 3.9%. And also the fraction of smaller molecular size below 0.5 kDa was increased from 4.8%(untreated HA) to 12.3%(in Ozone alone) and 40.1%(in Ozone/GAC) respectively at the reaction time of 120 min.

• Analytical Science and Technology
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• v.18 no.6
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• pp.535-541
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• 2005

The formation of aldehydes as by-product was investigated in the treatment of humic acid by Ozone/GAC hybrid process. Ozone/GAC hybrid process was operated under varying initial pH (pH 3~pH 11) and temperature ($0^{\circ}C$, $20^{\circ}C$, $40^{\circ}C$) at an ozone dose of 0.08 g $O_3/g$ DOC and GAC amount of 16.5 v/v%. The results were compared with those of GAC adsorption and ozone alone process. The formed aldehydes were derivatized by PFBOA method and quantified by GC/PDECD. Formaldehyde and glyoxal were identified as the substantial aldehydes in the treatment of humic acid by ozone/GAC hybrid process. Quantities of formaldehyde and glyoxal formed in ozone/GAC hybrid process were less than one in ozone alone process. In ozone/GAC hybrid process, formaldehyde was produced with a considerable concentration of 400 ppb at pH 11 and pH 7 at the beginning of the treatment, and then the concentration was decreased with time. And, the concentrations of formaldehyde and glyoxal were increased with an increase of temperature. They were respectively 520 ppb and 120 ppb at the beginning of the treatment at $40^{\circ}C$.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.47-52
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• 2008

In this study, GAC adsorption, ozonation and $O_3/GAC$ hybrid processes were investigated for treatment of humic acid. The degradation characteristics and efficiencies of humic acid in each process were evaluated through pH variation, $UV_{254}$ decrease, DOC removal, change of molecular size distribution and by-products formation. DOC removal rate in $O_3/GAC$ hybrid process (80%) was higher than arithmetic sum of ozonation (38%) and GAC adsorption process (19%) by synergism. $UV_{254}$ decrease rate of humic acid was also the highest than any other processes when treated in $O_3/GAC$ hybrid process. Molecular size distribution was not significantly changed in the GAC adsorption process. Main distribution of molecular size of humic acid was converted from 3 k~30 kDa into 0.5 k~3 kDa in ozonation. But the most of large molecular sizes of humic acid converted into small molecules(smaller than 0.5 kDa) in $O_3/GAC$ hybrid process. Quantities of formaldehyde and glyoxal formed in $O_3/GAC$ hybrid process were less than the ones in ozonation.